KONSTANZ - A new study from the University of Konstanz in Germany indicates that a variety of spiders may be capable of REM sleep and, perhaps, having dreams. In other words, while you're having nightmares about them, they could be dreaming of you, too.
According to the Cleveland Clinic, REM sleep is characterized by vivid dreams and the temporary inability to move major muscles, like those in the arms and legs. It usually arrives about an hour and a half after initially falling asleep. It is known to occur in mammals and birds.
However, this new research suggests the species evarcha arcuata might need to be added to the list. Behavioral ecologist Daniela C. Rößler kept a number of these spiders in plastic boxes on her windowsill and returned home one day to find them motionless, hanging from silk lines, reports Scientific American.
After further observation, Rößler and her fellow researchers found phases of rapid eye movement during this sleep-like period, 40 percent of which was accompanied by leg twitches. They were able to observe this eye movement because retinal tubes are much more visible in newly hatched spiders since pigment in the eyes' cuticles has yet to form.
Ars Technica says more research is needed before it's verified that spiders experience REM sleep since the phenomenon has significant implications and may complicate scientists understanding of the process.